It has previously been proposed--see the referenced German Patent Disclosure Document No. DE-OS 31 09 638, to which European Patent Application No. 0 060 325 corresponds--to provide an electronic control system, in form of a servo motor system, for electronic control of fuel being supplied to the ICE as the function of deflection of an operator pedal. Monitoring and control systems for such an electronic servo system are also known. In one such arrangement, as described in the referenced German Patent Publication, a potentiometer which forms an operator pedal position transducer, and coupled to the operator pedal, provides a command signal to a controller which receives from the potentiometer coupled to the throttle an actual signal value. The controller forms a difference or error signal which is applied, via an amplifier or power stage, to a positioning motor, coupled to the throttle, until the error signal becomes zero or null. This servo system, thus, electronically replaces the usual, previously used and quite customary throttle position change mechanism which, ordinarily, is mechanical, for example, by means of a Bowden cable, a linkage, or the like. The overall system, which may be termed an " electronic fuel controller" or "electronic fuel pedal" has the advantage that it is a simple matter to introduce modifying parameters into the electrical system which changes the throttle; this permits accurat and simple control of idle speed and/or control of dynamics of operation of a vehicle, for example upon rapid changes in acceleration, which can easily be carried out by electrical signals, being used to modify the control signals applied to the positioning motor, and entirely independently of position of the operator pedal.
A particularly important feature to be considered in an electronic operator pedal is the operating reliability thereof. Any electronic system which becomes complex will have a substantial number of components; as the number of components rises, the possibility of error or malfunction likewise increases. It is particularly important to consider malfunction or error in the operation of the position transducer, both of the transducer coupled to the operator pedal, as well as to the actual fuel control element, for example the throttle. Further, the drive, or positioning or servo motor which positions the throttle has to be carefully considered, since, by mechanical malfunction, wear and tear, contamination or dirt, errors and non-linear performance may result. It is known to associate the pedal and/or the fuel controller with limit switches at respective limiting positions, for example at idle or no-load and full-load or fully depressed pedal position, corresponding to fully open throttle, or maximum deflection of a fuel injection pump control element. By comparing signals from limit switches, it is possible to obtain logic conditions which may be permitted or are indicate of impossible or prohibited conditions, and thereby, if a prohibited condition is sensed, provide an error or malfunction recognition output.